The present invention relates to a carrier strip assembly as well as the interface between the lead pins on the carrier strip assembly and an electrical component package. More particularly, this invention relates to a carrier strip assembly which has round lead wires with integrally formed clamps on the free ends of the lead wires for connection to electrical component packages. The present invention is also directed to the method of fabricating the carrier strip or lead frame assembly having the round lead wires with integrally formed clamps on their free ends.
Inherent in the competitive environment of manufacturing electronic products is the utilization of low-cost rapid high volume manufacturing processes. A widely practiced approach to the assembly of electrical component packages having in-line pin devices for connection to various circuit assemblies or subassemblies is the attachment of a lead frame carrier or carrier strip assembly to the electrical component substrate to facilitate a continuous automated process. The carrier strip assembly includes the leads which are to be attached to the electrical component.
Generally, the carrier strip is made by stamping or etching some type of continuous band of thin gauge metal into a particular form wherein the strip becomes not only the carrying mechanism for the electrical component during its assembly, but also a source of the lead pins for the electronic component device. The typical presently used carrier strip assembly has the lead pins integrally formed thereon and they have a generally rectangular or square cross-sectional shape. However, in some instances it is desirable for the lead pins to have a round or circular cross-sectional shape.
It is recognized that in some electrical component modules straight rond lead wire pins have been utilized. However, these pins are generally affixed to the large area surface of the component substrate and are positioned along one edge of the substrate, so that the pin is offset from the centerline of the edge thickness of the substrate. In the construction of electrical component packages, having a substrate to which lead pins are connected, it is important that the longitudinal centerline of the pin be aligned with the centerline or center of the substrate edge thickness. Otherwise, the lead pins become offset from the center of the substrate edge thickness and present an unbalanced non-symmetrical lead pin arrangement with respect to the edge of the component package. This offset arrangement of the lead pins requires more room on the board assembly to which the component is attached. Also, the offset pins may cause more stress on the pin/substrate connection when the lead pins are inserted into a board assembly.
The typical rectangular cross-sectionally shaped lead pins which are formed on the carrier strip normally require the incorporation of tie bars adjacent the free ends of the lead wires to maintain their proper location with respect to each other. This necessitates the additional step of cutting away the tie bars after the component has been assembled.